Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $181.50   12.183%   $203.6121   $203.61   $203.60   $203.60  
  Purchase #2 $122.77   3.225%   $126.7293   $126.73   $126.75   $126.70  
  Purchase #3 $101.32   13.628%   $115.1279   $115.13   $115.15   $115.10  
  Purchase #4 $68.27   11.791%   $76.3197   $76.32   $76.30   $76.30  
  Purchase #5 $181.34   11.297%   $201.826   $201.83   $201.85   $201.80  
  Purchase #6 $191.44   5.704%   $202.3597   $202.36   $202.35   $202.40  
  Purchase #7 $121.47   4.216%   $126.5912   $126.59   $126.60   $126.60  
  7 purchase totals = $968.11       $1,052.5659   $1,052.57   $1,052.60   $1,052.50